U.S. patent application number 13/396370 was filed with the patent office on 2012-08-30 for rock bolt.
Invention is credited to Michael Bayerl, Richard Podesser.
Application Number | 20120219365 13/396370 |
Document ID | / |
Family ID | 45531183 |
Filed Date | 2012-08-30 |
United States Patent
Application |
20120219365 |
Kind Code |
A1 |
Podesser; Richard ; et
al. |
August 30, 2012 |
Rock Bolt
Abstract
A rock bolt, particularly for use in mining, having an axial
conduit, an anchor nut, and an anchor plate supported by the anchor
nut for the purpose of placement on the rock, that is able to
expand sufficiently and possess sufficient tensile strength, and
also is able to be cut for the purpose of simplified separation of
excavated pieces of the rock bolt. This problem is addressed in
that the axial conduit is at least partially, and particularly
entirely, made of metal and plastic, and the at least one component
of the axial conduit made of metal and plastic serves to receive
tensile forces.
Inventors: |
Podesser; Richard; (Buchloe,
DE) ; Bayerl; Michael; (Tuerkheim, DE) |
Family ID: |
45531183 |
Appl. No.: |
13/396370 |
Filed: |
February 14, 2012 |
Current U.S.
Class: |
405/259.1 ;
405/259.3 |
Current CPC
Class: |
E21D 20/025 20130101;
E21D 21/0046 20130101; E21D 21/0006 20130101 |
Class at
Publication: |
405/259.1 ;
405/259.3 |
International
Class: |
E21D 20/00 20060101
E21D020/00; E21D 21/00 20060101 E21D021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 14, 2011 |
DE |
102011004023.4 |
Claims
1. A rock bolt, said rock bolt including: an axial conduit; an
anchor nut; and an anchor plate supported by the anchor nut, for
the purpose of placement on the rock, wherein the axial conduit is
made at least partially of both metal and plastic, wherein at least
one component of the axial conduit, said component being made of
metal and plastic, serves to receive tensile forces.
2. A rock bolt according to claim 1 wherein the axial conduit, on
an inner segment of the axial conduit, is made at least partially
of both metal and plastic.
3. A rock bolt according to claim 2, wherein the axial conduit has
a front end and a rear end, and the inner segment is spaced from
the front and the rear ends at a distance of at least 5%, 10%, or
20% of the total length of the axial conduit.
4. A rock bolt according to claim 3 wherein the axial conduit is
constructed in multiple parts from components made of either
plastic and metal.
5. A rock bolt according to claim 4, wherein on the axial conduit
one component made of metal and one component made of plastic are
arranged in alternating sequence along the dimension of a
longitudinal axis of the axial conduit,
6. A rock bolt according to claim 4, wherein the axial conduit is
made of metal on the inner segment thereof, and does not have a
sheath made of plastic, and the at least one component made of
plastic is not a sheath of the at least one component made of
metal.
7. A rock bolt according to claim 6, wherein the plastic is
reinforced with fibers, and the metal is steel.
8. A rock bolt according to claim 7, wherein said fibers are
fiberglass
9. A rock bolt according to claim 4, wherein the at least one
component made of plastic is made of at least 50% plastic.
10. A rock bolt according to claim 4, wherein the at least one
component made of metal is made of at least 50% metal.
11. A rock bolt according to claim 1, wherein in a first section
which is perpendicular to a longitudinal axis of the axial conduit,
on the inner section, the axial conduit is made of at least 50%
plastic.
12. A rock bolt according to claim 1, wherein in a second section
which is perpendicular to a longitudinal axis of the axial conduit,
on the inner section, the axial conduit is made of at least 50%
metal.
13. A rock bolt according to claim 4 wherein the components are
connected to each other using an inner or outer plastic
sheathing.
14. A rock bolt according to claim 4 wherein fibers of the plastic
which is reinforced with the fibers are arranged on the component
made of metal, the fibers are saturated with a matrix material and
cured, and the component made of plastic is connected to the
component made of metal using the fibers.
15. A rock bolt according to claim 4 wherein the inner diameter of
one component corresponds substantially to the outer diameter of
another component, such that the other component is arranged
axially inside the component, and the two components are connected
using an adhesive bond to each other, and one component has an
inner threading, and another component has an outer threading, such
that both components are axially screwed into each other on the
inner and outer threadings thereof, and the outer diameter of one
component and, at least sectionally, the inner diameter of another
component are substantially the same, and the other component is
partially slid over the one component on an overlap region thereof,
wherein the two components are connected to each other using a
sheathing pressed onto the outside thereof on the overlap region,
and said sheathing is made of metal.
16. A rock bolt according to claim 1, wherein the axial conduit is
designed as a hollow tube.
17. A rock bolt according to claim 1, wherein the axial conduit
encloses an interior space, and the rock bolt has a fixing agent
arranged in the interior space for the purpose of fixing the axial
conduit on the rock with a material connection, a moving piston
arranged in the interior space for the purpose of conveying the
fixing agent to the outside of the axial conduit when the axial
conduit is arranged inside a bore hole in the rock, and at least
one structure for moving the piston.
18. A rock bolt according to claim 17, wherein a rear end of the
axial conduit is closed by a cap, and the axial conduit and/or the
cap have at least one opening for the purpose of conveying the
fixing agent out of the interior space enclosed by the axial
conduit.
19. A rock bolt according to claim 17, wherein a mixer is arranged
between the fixing agent and the at least one opening for the
purpose of mixing the fixing agent prior to the fixing agent
discharging from the at least one opening.
20. A rock bolt according to claim 1, wherein the rock bolt has an
expansion sheath and an expanding element.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to German Patent
Application DE 10 2011 004 023.4, filed Feb. 14, 2011, and entitled
"Gesteinsacker" ("Rock Bolt"), which is hereby incorporated by
reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] One or more embodiments of the present invention relate to a
rock bolt.
[0003] In the fields of mining and tunnel construction, rock bolts
are used to prevent or slow movement in the solid rock, or to
secure solid rock against larger-area flaking, thereby enabling
operation without danger. In this case, two functional principles
are known, and are also known in partial combination. In mechanical
systems, the bolt is anchored using a friction fit, wherein
mechanical rock bolts generally also have an expansion sleeve and
an expanding element. In the case of chemical rock bolts, an axial
conduit is connected to the substrate and/or the solid rock in a
material connection using a curable mortar or an artificial resin
used as a fixing agent. The rock bolts in this case are installed
in the solid rock with or without pretensioning. In contrast to
applications in tunnel construction, rock bolts used in mining,
e.g. in underground coal mining, serve to temporarily secure the
rock. This is because, in general, the temporarily secured rock
will be extracted in a later work phase, and the rock bolts will
then also be removed from the rock.
[0004] In mining and tunnel construction, rock bolts are used which
have an axial conduit, the same being particularly designed as a
hollow tube
[0005] In this case, the rock bolts are preferably made of
fiberglass reinforced plastic. The plastic reinforced with
fiberglass only expands to a minimal degree when the axial conduit
is subjected to tensile forces in the rock, and also possesses low
resistance to compression and to shearing forces. Due to the low
expansion capacity of the axial conduit made of
fiberglass-reinforced plastic, these rock bolts must be used in
high quantities and placed closely together to prevent any movement
of the substrate and to reduce the shearing forces applied to each
rock bolt. Due to the low resistance to compression and shearing of
the material, a large fraction of the rock bolts having the axial
conduit made of fiberglass reinforced plastic are damaged and/or
destroyed during the installation thereof due to the compression
forces and/or shearing forces involved. In coal mining
applications, such rock bolts having axial conduits which are
manufactured from fiberglass reinforced plastic are used in the
coal seam itself to secure the advancing section in front of a
longwall section. These rock bolts are extracted together with the
coal, but then cannot be removed from the coal, or can only be
removed with very great difficulty. Rock bolts having an axial
conduit made of steel are generally not used to secure coal seams
because they cannot be cut, and/or have sharp edges following
excavation of the coal. The rock bolts having an axial conduit made
of steel cut up the conveyor belts or destroy other devices used in
coal mining, thereby leading to high costs and interruptions. Rock
bolts used in coal mining which have an axial conduit made of
fiberglass reinforced plastic cause substantially no damage to
conveyor belts or other devices in the mine during excavation
because they can be cut easily, and therefore can be easily broken
up by the excavation equipment. However, these rock bolts possess
insufficient properties with respect to mechanical considerations
of expansion, resistance to compression, and resistance to
shearing. Rock bolts having axial conduits made of steel pose the
disadvantage that they cause damage to conveyor belts and other
equipment of the mine during excavation of the coal.
[0006] WO 2007/059580 A1 discloses a self-cutting rock bolt having
a cutting head and an axial conduit.
BRIEF SUMMARY OF THE INVENTION
[0007] The problem addressed by one or more embodiments of the
present invention is that of providing a rock bolt which possesses
sufficient capacity for expansion and tensile strength, and can be
cut to enable simplified separation of the excavated pieces of the
rock bolt.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Embodiments of the invention are described in greater detail
below with reference to the attached illustrations, wherein:
[0009] FIG. 1 shows a longitudinal section of a rock bolt which is
inserted into a bore hole, wherein the fixing agent has not yet
been inserted into the space between the rock and the axial
conduit,
[0010] FIG. 2 shows a longitudinal section of the rock bolt in FIG.
1, wherein the fixing agent has been inserted into the space
between the rock and the axial conduit,
[0011] FIG. 3 shows a longitudinal section of an axial conduit of
the rock bolt according to FIG. 1,
[0012] FIG. 4 shows a longitudinal section of a component of the
axial conduit according to FIG. 3, made of metal and plastic,
having a connection between the two components in a first
embodiment,
[0013] FIG. 5 shows a longitudinal section of the components of the
axial conduit according to FIG. 3, made of metal and plastic,
having the connection between the two components in a second
embodiment,
[0014] FIG. 6 shows a longitudinal section of the components of the
axial conduit according to FIG. 3, made of metal and plastic,
having the connection between the two components in a third
embodiment,
[0015] FIG. 7 shows a longitudinal section of the components of the
axial conduit according to FIG. 3, made of metal and plastic,
having the connection between the two components in a fourth
embodiment, and
[0016] FIG. 8 shows a longitudinal section of the components of the
axial conduit according to FIG. 3, made of metal and plastic,
having the connection between the two components in a fifth
embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0017] This problem is addressed by a rock bolt, particularly for
use in mining, having an axial conduit, an anchor nut, and a plate
supported by said anchor nut, said plate being for the purpose of
placement on the rock, wherein the axial conduit is made at least
partially, and particularly entirely, of metal and plastic, and
this at least one component of the axial conduit which is made of
metal and plastic serves to receive tensile forces.
[0018] The axial conduit of the rock bolt therefore is made of
metal, particularly of steel, and of plastic. As such, the axial
conduit can undergo larger expansions in the axial dimension when
tensile forces are applied thereto, such that the rock bolt is also
by design a directional anchor. In this way, movements which occur
in the secured rock can be secured against in an improved manner.
In addition, the axial conduit of the rock bolt can be easily
broken up and/or separated by mining machines in the mining
applications, particularly in coal mining applications, such that
damage can be substantially prevented to the technical equipment of
the mining operation.
[0019] The rock bolt particularly is made, in one inner segment of
the axial conduit, at least partially, and particularly entirely,
of metal and plastic.
[0020] In a further embodiment, the axial conduit has a front end
and a rear end, and the inner segment is distanced from the front
and the rear ends by a gap of at least 5%, 10%, or 20% of the total
length of the axial conduit. Therefore, the design of the rock bolt
as made of metal and plastic preferably does not involve the region
of the rock bolt in the proximity of the front and the rear
ends.
[0021] In a further embodiment, the rock bolt is constructed in
multiple sections of components made of plastic and metal. The at
least one component of the rock bolt made of plastic and the at
least one component of the rock bolt made of metal are initially
produced separately, and are connected to each other during the
manufacture of the rock bolt.
[0022] One component made of metal and one component made of
plastic are preferably arranged in an alternating manner along the
longitudinal dimension of the rock bolt, and/or the rock bolt made
of of metal has no sheathing made of plastic, particularly on the
inner segment, and the at least one component made of plastic is
particularly not a sheathing of the at least one component made of
metal.
[0023] In one variant, the plastic is reinforced plastic,
particularly plastic reinforced by fiberglass, and the metal is
steel.
[0024] The at least one plastic component is made advantageously of
at least 50%, 70%, or 90% plastic, and particularly is entirely
plastic, and/or the at least one component is made of at least 50%,
70%, or 90% metal, and particularly is entirely metal.
[0025] In a further embodiment, the rock bolt is made of at least
50%, 70%, or 90%, and particularly is made entirely of, plastic in
a first segment thereof, particularly in the inner segment as a
cross-section which is perpendicular to the longitudinal axis of
the rock bolt, and in a second segment, particularly in the inner
segment as a cross-section which is perpendicular to the
longitudinal axis of the rock bolt, the rock bolt is made of at
least 50%, 70%, or 90%, and particularly is made entirely of,
metal.
[0026] The components are particularly connected to each other
using an inner or outer plastic sheath, and/or fibers of the
reinforced plastic are arranged on the metal components. The fibers
are particularly saturated with a matrix material and then cured,
and the plastic component is connected to the metal component using
the fibers, and/or the inner diameter of one component corresponds
substantially to the outer diameter of another component, such that
the other component is arranged coaxially inside the component, and
both components are connected to each other by an adhesive bond,
and/or one component has an inner threading and another component
has an outer threading, such that both components are screwed into
each other via the inner and outer threadings, and/or the outer
diameter of one component and the inner diameter of another
component, preferably sectionally, are substantially the same, and
the other component is partially slid over the component on an
overlap region thereof, and then both components are connected to
each other by a sheath which is pressed onto the outside of the
same, said sheath particularly made of metal, e.g. steel.
[0027] In a further embodiment, the axial conduit is designed as a
hollow tube.
[0028] In a complementary variant, the axial tube encloses an
interior space, and the rock bolt has a fixing agent arranged in
the interior for the purpose of establishing a material, fixed
connection of the axial conduit to the rock, a movable piston
arranged in the interior of the fixing agent and outside the axial
conduit when the axial conduit is arranged in a bore hole in the
rock, and at least one system for moving the piston. The rock bolt
is therefore a chemical rock bolt.
[0029] In a further variant, a rear end of the axial conduit is
closed by a cap, and the axial conduit and/or the cap have at least
one opening for conveying the fixing agent out of the interior
space enclosed by the axial conduit.
[0030] In a further embodiment, a mixer is arranged between the
fixing agent and the at least one opening for the purpose of mixing
the fixing agent, particularly the two components thereof, prior to
the fixing agent exiting the at least one opening.
[0031] The rock bolt particularly has an expansion sleeve and an
expansion element. The rock bolt is therefore a mechanical rock
bolt.
[0032] Rock bolts are preferably also rock anchors.
[0033] In a complementary embodiment, the fixing agent,
particularly an artificial resin or mortar, has two components,
e.g. one adhesive component and one curing component.
[0034] The two components are preferably each arranged in separate
pouches. In this case, any device which contains the two separate
components is considered a pouch. For example, a cartridge or a
different type of container can be contemplated.
[0035] In a further embodiment, the rock bolt has a drilling head,
particularly in the region of the front end or on the front end of
the axial conduit. The rock bolt is therefore a self-cutting rock
bolt.
[0036] Referring now to the Figures, a rock bolt 1 designed as a
directional anchor 2 is used in mining applications for the purpose
of temporarily securing the rock in a gallery. The rock bolt 1 has
an axial conduit 3 which encloses an interior space 4. The rock
bolt 1 is a chemical rock bolt 1, meaning that the axial conduit 3
can be attached to the rock 28 in a material connection using a
fixing agent 5 arranged in the interior space 4. For this purpose,
a bore hole 29 is constructed in the rock 28, and the rock bolt 1
is then inserted into the bore hole 29. This process is portrayed
in FIG. 1, prior to the fixing agent 5 being pressed out into a
space between the axial conduit 3 and the rock 28. In FIG. 2, the
rock bolt 1 which is attached by a material connection to the rock
28 is illustrated. The fixing agent 5 in this case is an artificial
resin 6 which has an adhesive component 7 and a curing component 8.
The adhesive component 7 is contained in a first pouch 9, and the
curing component 8 is contained in a second pouch 10. Both pouches
9, 10 are contained in the interior space 9.
[0037] The interior space 4 has a hydraulic chamber 17 which is
closed by a ring piece 20 in the region of the outer, rear end 37
of the axial conduit 3. The ring piece 20 has a hydraulic bore hole
19. In addition, the hydraulic chamber 17 is bounded by a piston 11
in the region of a different, inner, front end 36. The inner, front
end 36 of the axial conduit 3 is closed by a cap 23 having an
opening 24. The fixing agent 5 can flow out of the interior space 4
of the axial conduit 3 through the opening 24 and out into the
space, particularly the annular space, between the rock bolt 3 and
the rock 28. In this case, a mixer 25 is arranged on the opening
24, and the fixing agent 5 must necessarily flow first from the two
pouches 9, 10 through the mixer 25, due to the geometrical
arrangement of the mixer 25 in the interior space 4, then the
fixing agent 5 flows out through the opening 24. In this case, the
mixer 25 has devices, by way of example a corresponding geometry,
such that the fixing agent 5 flows through the mixer 25 in a
circuitous or looping manner, achieving a mixing of the adhesive
component 7 and the curing component 8 of the artificial resin 6
prior to the same flowing out through the opening 24.
[0038] An anchor nut 14 is screwed onto the outer threading 18 in
the region of the outer, rear end 37 of the axial conduit 3, the
same having an outer threading 18, wherein said anchor nut 14 has
an inner threading and an anchor plate 15 lies on the anchor nut
14. The anchor plate 15 in this case has a plate boring 13 with no
inner threading, and the axial conduit 3 is arranged inside said
plate boring 13. In this way, pressure can be applied by the rock
28 according to the illustration in FIG. 2 onto the anchor plate
15. This pressure is transmitted by the anchor plate 15 to the
anchor nut 14, and then from the anchor nut 14 to the axial conduit
3, such that a tensile force acts on the axial conduit 3. This
tensile force is transmitted to the rock 28 by the axial conduit 3,
in a material connection with the fixing agent 5 on the outside of
the axial conduit 3.
[0039] For the purpose of introducing the fixing agent 5 into the
space between the axial conduit 3 and the rock 28, a piston 11 is
moved inward, meaning that, according to the illustration in FIG.
1, the piston 11 moves upward. In this manner, the first and the
second pouches 9, 10 are destroyed by the piston 11, such that the
adhesive component 7 and the curing component 8 move, and the
fixing agent 5 is pressed through the mixer 25 and through the
opening 24 into the space between the axial conduit 4 and the rock
28 due to the shrinking volume of the interior space 4 between the
piston 11 and the cap 23, and the fixing agent 5 subsequently
cures. For this purpose, a hydraulic fluid, e.g. water, is pumped
under high pressure into the hydraulic chamber 17 through the
hydraulic bore hole 19, thereby moving the piston 11. The hydraulic
chamber 17 and the hydraulic bore hole 19 are therefore a structure
12 for moving the piston 11.
[0040] In FIG. 2, the fixing agent 5 is already fully extruded into
the space between the axial conduit 3 and the rock 28, meaning that
the axial conduit 3 is attached to the rock 28 in a material
connection, particularly by using adhesive bonding. In the state of
installation illustrated in FIG. 2 in this case, the axial conduit
3 is substantially entirely arranged in the interior space 4,
meaning that only a small fraction of the axial conduit 3, by way
of example less than 10% or 5%, is present outside the interior
space 4. In this way, when the rock bolt 1 is installed, very
little space is required in the work space 30 in the mining
gallery. In the state of the rock bolt illustrated in FIG. 2, the
anchor plate 15 rests on the rock 28, and can therefore receive
compression forces. In addition, shearing forces applied
perpendicular to a longitudinal axis 38 of the axial conduit 3 can
also be received by the rock bolt 1, and the rock 28 can be
additionally secured in this manner.
[0041] In FIG. 3, a part of the axial conduit 3 is illustrated in a
longitudinal section as a hollow tube. The axial conduit 3 is made
of components 26 made of metal, particularly steel or a steel
alloy, and components 27 made of plastic, particularly a plastic
which is reinforced by fiberglass. In this case, these components
26, 27 made of metal and plastic are arranged in an alternating
configuration along the direction of a longitudinal axis 38 of the
axial conduit 3. In FIG. 3, the type of connection between the
component 26, 27 is not illustrated. The fibers 32 of the
fiberglass reinforced plastic of the components 27, said fibers 32
being not illustrated, have fibers 32 which are oriented in the
direction of the longitudinal axis 38 for the purpose of receiving
tensile forces exerted on the axial conduit 3, and have fibers 32
which are oriented at an angle to the longitudinal axis 38, by way
of example perpendicular thereto or at an angle of approximately
45.degree. to the direction of the longitudinal axis 38. The latter
fibers 32 constitute cross fibers and can receive torsional loads
exerted on the axial conduit 3. The components 26 made of metal
have a roughened surface 22 on the outer side thereof.
[0042] In FIGS. 4 to 8, different embodiments of the connection of
the components 26, 27 are illustrated. In the first embodiment,
according to FIG. 4, a plastic sheath 31 is applied by using
injection molding to both the components 26 made of metal and the
components 27 made of plastic. In this way, both components 26, 27
are connected to each other.
[0043] In the second embodiment, according to FIG. 5, fibers of the
fiberglass reinforced plastic of the components 27 are applied to
the outside of the components 26 made of metal. These fibers in
this case are saturated with a matrix material, for example an
artificial resin, and then cured. In this way, it is possible to
produce a load-bearing connection to the component 26 made of
metal, i.e. a steel component.
[0044] In this case, these fibers 32 are laid out as both
longitudinal fibers and cross fibers.
[0045] In FIG. 6, a third embodiment of the connection between the
components 26, 27 is illustrated. The inner diameter of one
component 26 corresponds in this case substantially to an outer
diameter of another component 27. Thus the inner and outer
diameters in this case substantially comprise a difference of less
than 10%, 5%, 2% or 1%. In this way, the component 27 as a plastic
part can be inserted coaxially into the component 26 as a steel
part. By using adhesive bonding 33, both a material connection and
a positive-fit connection can be produced between the components
26, 27.
[0046] In the fourth embodiment illustrated in FIG. 7, the
component 26 has an outer threading, and the component 27 has an
inner threading, both indicated as the threading 34. In this way,
the two threadings 34 can be screwed together, thereby producing a
connection between the two components 26, 27.
[0047] In FIG. 8, a fifth embodiment of the connection between the
components 26, 27 is illustrated. The fibers 32, particularly the
fibers laid out as longitudinal and cross fibers, are applied in
this case to the outside of the component 26. These fibers 32
applied to the outside of the component 26 are pressed or clamped
to each other by using a sheath 35, particularly a steel sheath 35.
The sheath 35 is therefore pressed onto the fibers 32 or is
designed with a conical shape and/or is screwable, for the purpose
of generating a radial pressure between the fibers 32 and the outer
side of the component 26 made of metal.
[0048] The axial conduit 3 therefore has, in alternating sequence,
the steel parts 26 and/or components 26 made of steel, and the
plastic parts 27 and/or the components 27 made of plastic. After
the rock bolt 1 is fixed in the bore hole 29 and/or on the rock 28,
the tensile forces are received by the axial conduit 3.
[0049] In this case, the components 26 made of metal, particularly
of steel, have high expansion upon the exertion of tensile forces,
such that a large overall expansion occurs in the axial conduit 3
when high tensile forces are exerted on the same. This happens
because a substantial fraction of the axial conduit 3 is made of
the components 26. In this case, the components 26 comprise at
least 30%, 50%, or 70% of the total expansion of the axial conduit
3, preferably in the direction of the longitudinal axis 38. In this
way, the rock bolt 1 is also a directional anchor, and as such has
a sliding function such that small movements in the secured rock 28
can be received due to the length modification of the axial conduit
3 in the form of elongation. As such, movements of the rock 28 are
permitted by the rock bolt 1. In this way, it is possible to
substantially prevent the axial conduit from breaking
unexpectedly.
[0050] The rock bolt 1 will be used substantially in mining,
particularly coal mining. In the case of application in mining, the
rock bolt 1 is used for the purpose of temporarily securing the
solid rock 28, and particularly coal. The coal is excavated using a
shearer or a coal plow. During this excavation, the rock bolts 1
are also removed with the coal and/or in the rock 28, and can be
broken up by the shearer or the coal plow, and thereby transported
away, because the components 27 made of plastic can be easily
separated by the shearer or the coal plow. In this way, following
excavation, only small partial pieces of the axial conduit 3
appear, and these can be easily transported by the conveyor system.
Due to the fraction of metal also present in the components 26, the
same can be easily separated by a magnetic separator. Moreover, it
is also possible to separate the bolt pieces made of metal from the
coal in a wash plant, because the two materials have largely
different densities.
[0051] In a further, not illustrated, embodiment of the rock bolt,
the rock bolt substantially comprises only the axial conduit 3, the
anchor nut 14, and the anchor plate 15. In this case, the axial
conduit 3 is not designed as a hollow tube, but rather as a solid
profile.
[0052] When this rock bolt 1 is inserted into a bore hole 29, a
fixing agent 5 is first inserted into the bore hole 29, and the
axial conduit 3 is then inserted into the bore hole 29. In this
manner, the fixing agent 5 is distributed in a space between the
axial conduit 3 and the bore hole 29. In this case, the fixing
agent 5 can also have been inserted into the bore hole 29 in at
least one pouch 9, 10 prior to the insertion of the axial conduit
3.
[0053] As a whole, the rock bolt 1 according to an embodiment of
the invention involves substantial advantages. Due to the use of
metal, the axial conduit 3, having components 26, 27 made of metal
and plastic, comprises a sufficiently high expansion in the event
of tensile forces exerted on the same following the installation of
the rock bolt 1 into the bore hole 29, such that it is possible to
substantially prevent an unexpected break of the bolt. In addition,
the axial conduit 3 can receive large compression forces exerted
during the insertion of the same into the bore hole 29. Both the
components 26 made of metal and the components 27 made of plastic
have high resistance to compression, meaning that said components
26, 27 can receive large compression forces exerted in the
dimension of the longitudinal axis 38. In the case of rock
excavation 28, particularly of coal, the axial conduits 3 can be
easily severed due to the exclusive use of components 27 made of
plastic along the longitudinal dimension 38. In this way, it is
possible to reduce damage to the excavation equipment in the
mine.
[0054] While particular elements, embodiments, and applications of
the present invention have been shown and described, it is
understood that the invention is not limited thereto because
modifications may be made by those skilled in the art, particularly
in light of the foregoing teaching. It is therefore contemplated by
the appended claims to cover such modifications and incorporate
those features which come within the spirit and scope of the
invention.
* * * * *